As a temperature-sensitive-discoloration hydrogel based on NIPAAm/HHPC was fabricated via two steps of electron beam radiation. Small nanomaterial such as GO and Fe2O3 were also added severally into the system of hydrogel as chromogenic agent. Different colors can be displayed in nanocomposite hydrogel system at the low, medium and high temperature respectively. The LCST of hydrogel system can be also adjusted precisely by the changes of irradiation dose of the prepolymer and composition ratio. Experimental results showed that the hydrogel can be changed quickly itself color in its near LCST. The microstructure and composition of nanocomposite hydrogel were characterized further by NMR, FTIR, TG, DSC, XRD, FE-SEM and XPS so as to reveal the mechanism of temperature-sensitive- discoloration. The novel NIPAAm/HHPC-based nanocomposite hydrogel is suitable especially to indicate different fever temperatures for fever patients and can be expected to as a new type of temperature-sensitive sensor and replace the traditional clinical thermometer.
Graphical abstract (A) SEM images of different hydrogels (previous row). (B) The reversible temperature-sensitive-discoloration process of different hydrogels ( bottom left ). (C) DSC thermograms of different hydrogels ( bottom right ).
The uniform structural pores architecture in nanoscopic domain of ordered mesoporous silicas, such as MCM-41 and SBA-15, can be used as a confined space to produce nanomaterials with controlled dimensions and cylindrical shape. In this study, we report the synthesis of a ternary nanocomposite constituted of silver nanoparticles and polyaniline concomitantly produced in the presence of SBA-15. The synthetic process involved firstly the adsorption of aniline vapor into the silica pores followed by its polymerization by reacting with the silver salt (AgN(SO2CF3)2) solubilized in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (BMImTf2N). With this synthetic approach the reaction proceeded quickly and efficiently, generating the silver-polyaniline nanocomposite mainly into pores and without collapsing the silica mesostructure. Surface area and pore volume of SBA-15 decreased after the reaction proceeded, indicating the formation of polyaniline and silver nanoparticles composite inside the pores and complementary analysis evidenced the presence of some silver nanoparticles outside pores. The measured electrical conductivity of the ternary composite in the order of 10?6 S cm?1 was coherent to the presence of the polymer and silver nanoparticles inside the pores of the insulator SBA-15 mesostructure rather than on the surface of the particles. The prepared SBA-15 ternary nanocomposite presented higher silver nanoparticles loadings of and superior surface area than the ones observed to small pore silicas, such MCM-41. The improvement in textural properties of the nanocomposite are favorable aspects for the further development of sensors and catalysts.
Polyaniline/Multiwalled carbon nanotubes (PANI/MWCNTs) nanocomposite was prepared via liquid-liquid interfacial polymerization method. The morphology studies of the nanocomposite using SEM and TEM techniques confirmed the presence of PANI as aggregates along with MWCNTs and X-ray diffraction studies indicated the presence of graphitic planes of MWCNTs along with PANI in semi-crystalline emeraldine salt form. The PANI/MWCNTs nanocomposite electrode exhibited specific capacitance (Cs) of 1551 F/g at a scan rate of 2 mV/s in aqueous 1 M H2SO4 in a potential window of 0–1.2 V. The material exhibited good cycle life with 95% capacitance retention in a life cycle test conducted at 5 A/g for 1000 cycles. Further, an asymmetric supercapacitor device (ASD) was fabricated using PANI/MWCNTs as positive and activated carbon as negative electrodes in aqueous 1 M H2SO4. The ASD exhibited a Cs of 142 F/g at a scan rate of 5 mV/s in a wide potential range of 0–1.6 V. The device offered high energy and power densities of 29 Wh/Kg and 7.3 kW/Kg respectively and also demonstrated an excellent cyclic stability by retaining 97% of its initial capacitance after 5000 cycles at high current density of 20 A/g.
To realize the controlled release property, lower cytotoxicity, and long-term bioactivity of tetracycline, the chitosan hydrogel had been prepared using genipin as the cross-linker and the tetracycline was in situ encapsulated. The formation process and strength of hydrogel were studied by rheological analysis, and the microtopography was observed by scanning electron microscope. It was found that the amount of genipin could modulate the physical property of the hydrogel. For in vitro release and antibacterial assays, the hydrogel could controllably release tetracycline and keep its bioactivity for a long time. The tetracycline-loaded chitosan hydrogel showed good antibacterial effect even under alkaline environment, which displayed better stability compared with free tetracycline. Moreover, the tetracycline-loaded chitosan hydrogel exhibited lower cytotoxicity than did tetracycline alone, suggesting that this tetracycline-loaded chitosan hydrogel could be a more useful dosage form than separate doses of tetracycline. The novel aspects of this study include the cytotoxicity study and the in vitro and in vivo assays, which might be useful for other researchers in this field.
Graphical abstract To realize the controlled release property, lower cytotoxicity, and long-term bioactivity of tetracycline, genipin cross-linked chitosan hydrogel was used as the carrier of tetracycline. The hydrogel could controllably release tetracycline with bioactivity. The hydrogel showed good antibacterial effect even under alkaline environment. The hydrogel exhibited lower cytotoxicity than did tetracycline alone.
In this study, we aim at facile fabrication of biodegradable polyester nanocomposite films with homogenous dispersion of ZnO nanoparticles. An environment friendly multi-functional biodegradable polyester resin has been synthesized using polyethylene glycol (PEG), lactic acid (LA) and maleic anhydride (MA) as monomers. ZnO nanoparticles were synthesized by hydrothermal method. As prepared nanoparticles were characterized by particle size analyzer, FE-SEM (Field emission scanning electron microscopy) and TEM (Transmission electron microscopy). Biodegradable ZnO/polyester composite films with 0.25, 0.50, 0.75 and 1.0 wt% of ZnO nanoparticles were fabricated by solution casting method. Experimental results revealed that incorporation of ZnO nanoparticles lead to substantial improvement in UV protection, antimicrobial behaviour and thermal stability, while retaining the biodegradable nature of the films.
Here, a high breaking strength and high initial modulus fibers comprised of polyvinyl alcohol (PVA) and graphene oxide (GO) were fabricated via simple method of solution blending and wet-spinning. The structure and properties of these fibers were studied in details using two-dimensional X-ray diffractions, differential scanning calorimetry, one-dimensional X-ray diffractions, scanning electron microscopy, transmission electron microscopy, dynamic mechanical analysis and tensile test. Compared with pure PVA fiber, a 43 % improvement of breaking strength and an 81 % improvement of initial modulus were achieved by addition of 0.1 wt% of GO, and the results indicated that crystallization and orientation of GO/PVA composite fibers were both increased. GO could not only promote PVA chains ordered arrangement for increasing crystallization, but also act as a template for polymer amorphous orientation via the interactions between PVA and GO in the process of hot drawing and heat setting, which were responsible for the significant improvement in the mechanical properties of GO/PVA composite fibers.
Graphical abstract GO could not only promote PVA chains ordered arrangement for increasing crystallization, but also act as a template for PVA amorphous orientation in the process of hot drawing. The amorphous orientation degree and the crystallization degree of PVA fibers were increased by adding GO.
The babassu coconut is a plant very abundant in northeast of Brazil and other countries, and any part of plant and fruit becomes residue. In this study, babassu mesocarp (Orbignya sp) (BM) was chemically modified with phthalic anhydride (BMPA) to increase its solubility in an aqueous medium, and thus facilitate its processing in the form of thin films. The reaction of modification of the babassu mesocarp with phthalic anhydride (PA), obtaining BMPA, was confirmed by FTIR, XRD, TG/DTG, Zeta Potential and SEM analysis, from the differences in the bands of the FTIR spectra, increase in crystallinity, new thermal profile, changes in zeta potential value and morphology, respectively. The thin monolayer films of BM and BMPA were produced by the self-assembly monolayer (SAM) technique, and adsorbed onto conductive glass substrates (tin-doped indium oxide, ITO). The electroactive properties of these thin films were evaluated by cyclic voltammetry (CV). BM exhibited a pair redox pair process of +0.57 V(oxidation) and?+?0.19 V (reduction) for BM. In BMPA these redox processes were observed at +0.37 V (oxidation) and 0.24 V vs. ECS (reduction), verifying that both BM and BMPA are electroactive materials that can be used in the construction of sensor platforms, without the necessity of being conjugated with other electroactive materials, such as conductive polymers, metal phthalocyanines, or dyes. Furthermore, under the experimental conditions used, the BMPA presented a more reversible redox process and higher electrochemical stability in comparison to BM. This effect occurs because BMPA has higher solubility in aqueous media, which favors the preparation of films with smaller grain sizes compared to BM films, as observed by Atomic Force Microscopy (AFM). This study showed that BMPA is a new material with potential for applications in electrochemical sensors.
A series of new waterborne polyurethanes (WPUs) was successfully prepared by the prepolymer process from the bio-renewable sources hydroxytelechelic natural rubber (HTNR with MW 3000 g mol?1) and hydroxylated rubber seed oil (HRSO), with DMPA fixed at 5.6 wt%. The effects of ratio of HTNR and HRSO (ranging from 1.00/0 to 0.10/0.90) and of hydroxyl value (OHV) of HRSO (200 or 270 mgKOH/g) on final properties were studied. It was found that the particle size of WPU increased significantly with both HRSO/HTNR ratio and OHV of HRSO. Chemical structure of the WPU films was confirmed by FT-IR. The water uptake, mechanical, dynamic mechanical properties and thermal stability of WPU film improved with both HRSO content and OHV of HRSO, while swelling in THF decreased. All these WPU films had similar Tg. This article reports novel green biobased WPU with promising applications as adhesive for shoe industries.
We present a first report for developing stimulus responsive hydrogels via free radical aqueous polymerization technique using Acrylic acid (AAc), methacrylic acid (MAAc) and diethylaminoethyl methacrylate (DEAEMA). The morphological aspects of poly(AAc-co-DEAEMA) (pAcD) and poly(MAAc-co-DEAEMA) (pMcD) were investigated to delineate the relevant mechanism of hydrogel formation for better understanding of their mechanical behaviour. The formulated hydrogels were found to have a structural framework comprising inter-connected nanogels and continuous outer skin with macroporous interiors. An abrupt increase in the peak intensities specific to the polymer and a simultaneous decrease in the water related peaks in the attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra exhibited the phenomenon of phase separation, whereas peaks of proton nuclear magnetic resonance (1HNMR) revealed hydrogen bonding and electrolytic complexation between the monomers. Biocompatibility is the hallmark for any drug carrier and was evaluated by both in vitro and in vivo testing. Administration of the prepared hydrogels to rat models did not cause any significant affect on the vital organs.
Graphical abstract Graphical representation showing macroporous interior with interlocked nanoglobules as stable building blocks in pAcD gels with high in-vitro and in-vivo biocompatibility
A series of salicylaldimine ligands 2-tert-butyl-6-((2,4-bis(diphenylmethyl)-8-arylnaphthalen)imine)-phenol (L1: Aryl =4-tBu-phenyl; L2: Aryl = p-tolyl; L3: Aryl = phenyl; L4: 4-CF3-phenyl) and the corresponding neutral salicylaldimine nickel complexes (Ni1-Ni4) were prepared and characterized. In ethylene polymerization at 20 °C, these nickel complexes are highly active, with activities of up to 6.88 × 105 g·mol?1·h?1. Moreover, the molecular weight of the polyethylene could reach up to 8.1 × 105. Comparing with the classic salicylaldimine nickel complexes Ni5 at 20 °C, complexes Ni1 with the 4-tBu-phenyl substituent demonstrated 8 times higher activity and 35 times higher polyethylene molecular weight.
A method for the synthesis of particle brushes by grafting polylactic acid onto TiO2 nanoparticle is reported. The efficiency of grafting was enhanced by combining azeotropic separation of water with polycondensation in a single pot. PLA/TiO2 brushes synthesized with different ratio of lactic acid and TiO2 were characterized by various techniques such as FT-IR, XRD, TEM, XPS, 1H and 13C NMR. TEM analysis indicates that the sizes of TiO2 nanoparticles are between 2 and 8 nm. DLS was used to determine overall size of particle brush and average size varied between 59.68–65.83 nm. Zeta potential measurement indicated high stability of water dispersed particles brushes with measured values of ?30.1 to ?37.1 mV for brushes prepared with PLA/TiO2 ratio of 50:1 and 20:1 respectively. The DSC and TGA analysis showed that PLA/TiO2 nanocomposites have good thermal stability.
In this study, the effect of crosslinking conditions was investigated to obtain insoluble poly(ethylene oxide) (PEO) nanofiber mats having an ultraviolet (UV) initiating and crosslinking agent, pentaerythritol triacrylate (PETA), with various ratios in the presence or absence of UV irradiation at 366 nm. At first, PEO nanofibers were electrospun from 400,000 and 600,000 g/mole molecular weights of PEO and they were compared in terms of diameter and fiber morphology. Whereas applied voltage in the range of 10–25 kV had no significant effect on the fiber morphology, fiber diameters varied by voltage. An increase in the flow rate from 0.25 to 1.00 mL h?1 had an effect in favor of fabricating thicker fibers. The effect of distance to collector on the diameter and morphology was not distinctive. Fibers having irregular morphology and beads appeared with increasing the polymer concentration from 4 to 8 % w/v. Prior crosslinking, electrospinning process at selected conditions was applied to the PEO (600,000) including PETA and PEO-PETA nanofibers were obtained. Besides PETA concentration and UV application, drying conditions before UV irradiation were also found effective to obtain stable fibers in aqueous media. PEO nanofibers electrospun in the presence of 10 % PETA (w/w), dried for 8 days at 37 °C in an air atmosphere and then, irradiated with UV for 50 min were found most stable in aqueous media. However, crosslinking was also achieved in the absence of UV.
A highly conductive and reinforced polypropylene/nickel coated glass fiber (PP/NCGF) composite is fabricated via a simple and efficient strategy. Nucleating agent induced crystallization leads to the sharp volume excluded effect and drives NCGFs into the amorphous region of PP matrix, thus the formation of conductive network connected by NCGFs is promoted remarkably. The incorporation of nucleating agent dibenzylidene sorbitol (DBS) improves the strength of composites simultaneously due to the enhanced crystallinity and the reinforced interfacial interaction. Accordingly, the percolation threshold of PP/NCGF composites is decreased to 0.35 vol% (Ni content) by loading DBS, and the conductivity increases by four order of magnitude around the percolation threshold which exceeds 70 S/m with the Ni content of only 0.47 vol%. The tensile strength of PP/NCGF composites is increased by about 30–40 % in all range of NCGF content. This exciting result provides a strategy to prepare high-performance conductive composites by crystallization-induced enhancement.
Graphical abstract Nucleating agent induced crystallization leads to the sharp volume excluded effect and drives Ni coated glass fibers into the amorphous region of PP matrix, thus the formation of conductive network is promoted remarkably. The incorporation of nucleating agent improves the strength of composites simultaneously due to the enhanced crystallinity and the reinforced interfacial interaction.
The CO2 capturing and sequestration are of importance in environmental science. A new type of microporous coordination polymer (Ni/PAPy) with secondary amine groups has been successfully prepared. Taking advantage of the synergistic effect of metal-electrostatic and hydrogen bonding interactions between the Ni/PAPy network and CO2 molecules, the CO2 uptake capacity of the microporous coordination polymer reaches up to 4.82 mmol g?1 (1.0 bar, 273 K) with the high selectivities (CO2/N2?=?83, CO2/CH4?=?16), making the Ni/PAPy a promising microporous material for application of CO2 uptake and separation. For comparison, the microporous coordination polymer without secondary amine groups (Ni/PPy) is also prepared.
Graphical Abstract Taking advantage of the synergistic effect of metal-electrostatic and hydrogen bonding interactions between the Ni/PAPy network and CO2 molecules, the Ni/PAPy can be considered as a promising microporous material for application of CO2 uptake and separation.
The main objective of this study was to prepare thin film nanofibrous composite (TFNC) membranes based on self-support nanofibrous mats. To this end, polyethylene terephthalate nanofibrous supports were produced by electrospinning technique and subsequently heat treatment was performed to increase mechanical stability of the mats. Then, interfacial polymerization procedure was applied for preparation of TFNC nanofiltration membranes. For comparison, the thin film composite (TFC) nanofiltration membrane was prepared by the same conditions based on polyethersulfone ultrafiltration membrane prepared through phase inversion method. Chemical structure, morphology and mechanical properties were studied by using ATR-FTIR, SEM and tensile tests, respectively. Also, filtration performance was investigated by water flux, rejection, water contact angle and MWCO determination. Results showed that the TFNC nanofiltration membrane had higher salt rejection and four times higher water flux than the TFC nanofiltraion membrane (Na2SO4 rejection and pure water flux were (93 ± 3)%, (34 ± 2.3) L./m2h and (67 ± 4)%, (8 ± 0.9) L./m2h for TFNC and TFC, respectively). At the end, the filtration performance of PET TFNC-NF membrane was compared with other nanofibrous nanofiltration membranes.
Methanol permeation and conductivity of membrane materials are important factors to evaluate the feasibility of application as proton exchange membranes (PEMs) in direct methanol fuel cell (DMFC). The methanol permeation values of these composite membranes based on ionic liquids of trifluoroacetic propylamine (TFAPA) and the disubstituted imidazolium cations with different anions were summarized, and the methanol permeation behaviors were investigated in this work. Although these polymer/ionic liquid composite membranes displayed satisfactory conductivities, the relative selectivity values of conductivity to methanol permeability were lower than the value of Nafion® membrane. Moreover, polymerized ionic liquids (PILs) membranes showed the strong ability to hinder methanol permeation with a value around 10?11 cm2/s at 10 M methanol solution. The maximum relative selectivity value reached (2.23–1.76) × 106 S·s/cm3 for PVC-MIMCl membrane, which was near two orders of magnitude higher than the reported 2.47 × 104 S·s/cm3 for Nafion-117 membrane at 2 M methanol solution.
The G0 and G1 polyurethane dendrimers terminated with 3–12 atom transfer radical polymerization (ATRP) initiators were prepared using single and dual functional ATRP reagents and their structures were confirmed using FT-IR, 1H–NMR, HR-MS and SEC-MALLS techniques. 4-Vinylpyridine was polymerized using the G1 dendritic initiators to obtain six- and twelve-arm star poly(4-vinylpyridine)s (STAR-P1 and STAR-P2). The absolute molecular weight and PDI of star polymers were in the order of 105 and 1.23–1.24 respectively. Hydrolysis leading to degradation of inner polyurethane core of the star polymers yielded more narrow dispersed poly(4-vinylpyridine) chains and the SEC-MALLS data of these chains confirm the accurate control on number of arms. Both of the polymers were doped with KI/I2 along with N3-dye to work as efficient polymer electrolytes for dye sensitized solar cell (DSSC). The increment in the conductivity of doped STAR-P1 was very significant and reached 2.415 mS/m from 0.0066 mS/m of dopant salt. The current-voltage characteristics of these doped polymer electrolytes measured under simulated sun light with AM 1.5 at 40 mW/cm2 yielded energy conversion efficiency (η) of 5.13% and 1.90% for STAR-P1 and STAR-P2 respectively and these values also significantly high compared to 1.09% corresponds to current-voltage curve of the device fabricated without the polymers.
Graphical abstract Star poly(4-vinylpyridine)s were prepared using novel dendritic ATRP initiators and used as electrolytes for dye sensitized solar cell (DSSC); one of the cells showed 5.13% energy conversion efficiency.
We have mimicked the biofilm formation with highly stable biocompatible poly(2-methyl-2-oxazoline)-based polymersomes by simple spreading-drying of a droplet of the sample solution onto a glass support. The diffusion-limited aggregation process of polymersomes onto the surface was analyzed within a fractal framework. The different examples analyzed and presented together indicate one means by which the aggregation process can be controlled and predicted. The anti-bacterial adhesion properties of poly(2-methyl-2-oxazoline) allow potential uses in surface modification for biofouling prevention improving stability and response time.
A new approach to the preparation of hydrophobic porous polymers has been proposed. Three series of porous polymers which pores equally well-absorbed as water and organic liquids (benzene and iso-octane) were synthesized by visible light polymerization from compositions based on three different dimethacrylic esters with n-butanol. Three block copolymers based on N-vinylpyrrolidone and 2,2,3,3-tetrafluoropropyl methacrylate, differing in the length of the poly-(2,2,3,3-tetrafluoropropyl methacrylate) block, were synthesized for the purpose of hydrophobization of such porous polymers. A distinctive feature of synthesized block copolymers is that they are soluble only in methanol. It has been found that the treatment of porous polymers only with 2 wt.% of block copolymer methanol solution leads to a decrease water uptake by an order of magnitude, and the absorption of organic liquids does not change. In the course of the study it was possible to obtain a hydrophobic porous polymer sample that has water contact angle θ?=?121° and a low value of the polar component of the surface Gibbs energy (\( {\gamma}_s^p=0.2 \) mJ·m?2). The fundamental possibility of using such material for purification of organic liquids from water is shown.
Biodegradable polymers are identified as substantial materials for biomedical applications. These polymers have the ability to deteriorate through an unpretentious hydrolysis and eliminated through kidneys’ functions or metabolic processes. Among widely used biodegradable polymers in biomedical applications, poly(lactic acid) (PLA) is becoming one of the most paramount polymers. Synthesizing PLA through melt/solution polycondensation polymerizations makes it relatively easy to tailor properties of final product. However, their synthesis reactions are affected by several parameters such as polymerization time, temperature, pressure, catalysts, and the polarity of the solvent. Moreover, equilibrium reactions are controlled through utilizing a hydrophilic monomer such as ethylene glycol (EG). These factors can strongly impact final properties of PLA. Thus, it is indispensable to comprehend the effect of operating parameters during the polymerization process. Optimizing synthesis conditions can be accomplished through reducing side reactions. Furthermore, this can be achieved through racemization by utilizing chain extenders to build high molecular weight and enhance thermal stability. In this review, the design and fabrication of porous PLA scaffolds and their physicomechanical behavior are reviewed. Different PLA scaffold parameters were investigated thoroughly, which include biocompatibility, biodegradability, and mechanical properties for different porosity and pore sizes to mimic the complex architecture of the natural tissue regeneration.
